Photographic emulsion



Feb. 3, 1942. CARROLL 2,271,623

PHOTOGRAPHIC EMULSION Filegi Feb. 29, 1940 DENSITY g WAVELENGTH (mp)BURT .H. CARROLL INVENTOR Byyg ATTOR YS Patented Feb. 3, 1942 am 11.Carroll, Rochester, 1v. 2., to"

Eastman Kodak Company, Rochester, -N.' -Y.,'a'.

corporationoi'hlcwJcrseyv Application February 29, 1940, Serial uni-earsIn Great Britain March 30, 1939 19 Claims. 95-71) This invention relatesto photographic emulsions and more particularly to photographicemulsions of the silver halide type.

It is known that the inherent sensitivity of photographic silver halideemulsions (whether spectrally sensitized or not) can be enhanced, andthere has been a constant eifort to, produce higher speeds inphotographic emulsions. For example, it is known that the speedof'gelatinosilver-halide emulsions'can be enhanced by an extendeddigestion or ripening of the emulsion.

It is also known that the speed of silver halide emulsions (spectrallysensitized or not) can bev enhanced by incorporating in the emulsionscompounds containing a divalent atom of the sulfur group directly joinedby a double bond to a single metalloid atom to which is attached atleast another group of atoms. Examples of such compounds are allylisotliiocyanate andallylthiourea.

I have now found that the speed of photographic silver halide emulsionscan be increased by incorporating in the emulsions (spectrallysensitized or not) surface active substances, such as aqueous dispersingor wetting agents for example, of the cationic ammonium salt type.(Surface active substances are classified as anionic and cationic ornon-ionic, depending upon whether or not the substances ionize, and ifso, depending upon whether the anion or the cation is surface active.Surface active materials are sometimes referred to as capillary activematerials, lipophyle materials or materials which possess interfacemodifying properties.)

My new method of sensitizing emulsions is an improvement over the knownmethods of enhancing sensitivity, since the speed increases attained bymy new method are complementary to the speed increases that can beattained by the prior methods.

The surface-active substances act on the emulsion in unknown manner toincrease its effective sensitivity. As a result, the sensitivity isincreased by about the same amount at any wavelength within the range ofits spectral sensitivity, although in spectrally sensitized emulsionsthere is frequently observed an appreciable increase in relativesensitivity for longer wavelengths. Inasmuch as the silver ion andhydrogen ion concentration in my emulsions appear to undergo little orno change by virtue of the presence of the surface active substances, Ishall refer to the action of the surface active substance as a kind ofsupersensitization, and I shall refer to mixtures of the surface activesubstances and spectral (optical) sensitizers as combinations, althoughI do not intend to imply that the surface active substance and thespectral sensitizer are chemically combined.

My new supersensitized emulsions are an improvement over emulsionsknown:

in the art. The increases in sensitivity which can be attained withsupersensitiz'ingcombinations of dyes can be enhanced by my new method.Furthermore, whereas with supersensitizing combinations of sensitizing'dyes- (see United States Patents 2,075,046, 2,075,047, and 2,075,048,each dated March 30, 1937), the supersensitizing effect is confined moreor less to a single spectral region, the supersensitization attained inmy new emulsions extends throughout the entire region in which thespectral sensitizer acts (and is fairly uniform in degree throughout theentire region), while at the same time the sensitivity in the violet andblue region (where the spectral sensitizer does not act) is alsoenhanced about to the same degree.

An object of my invention, therefore, is to provide new photographicemulsions. A further object is to provide emulsions sensitized with a.

- supersensitizing combination of a sensitizing dye and a surface activematerial. A further object is to provide a process for preparing suchemulsions.

According to my invention, I incorporate in a photographic silver halideemulsion a cationic surface active ammonium salt substance. The surfaceactive substance can be incorporated in any suitable form, e. g. in theform of a solution in a suitable solvent, such as water or methylalcohol. The surface active material should b thoroughly incorporated inthe emulsion. The surface active substance can be added to the finishedemulsion or at any stage of the preparation of the emulsion.

In the case of spectrally sensitized emulsions, the surface "activesubstance can be incorporated in the emulsion before, simultaneouslywith, or,

after the sensitizing dye, although in some cases, as hereinafter setforth,it is advantageous to incorporate the sensitizing dye beforeincorporating the surface active material. The methods of incorporatingsensitizing dyes in emulsions are, of course, well known to thoseskilled in the art. Ordinarily, it is advantageous to employ asolutionof the sensitizing dye in a suitable solvent, e. g. methyl alcohol.Ethyl alcohol or "acetone may be employed in cases where the solubilityof the sensitizing dye in methyl alcohol is very low.

sensitizing dyes are ordinarily incorporated in the washed finishedemulsions, and in accordance with my invention, the surface activesubstances are advantageously also incorporated in the washed finishedemulsions. However, the surface active substance canbe added to theemulsion during the preparation thereof, i. e. during the precipitation,the first digestion or the second digestion (the ripening). Afterpreparing the emulsions in the presence of the surface active substance,the sensitizing dyes can be incorporated in the so-prepared emulsion.

As cationic ammonium salt surface active substances, I have found thatthose which do not contain a hydrogen atom on the ammonium nitrogen atom(i. e. the so-called quaternary ammonium types) are advantageouslyemployed.-

As cationic quaternary ammonium salt surface active substances, Iinclude particularly those having at least one lipophylic quaternaryammonium cation containing four separate alkyl groups (alcohol radicals)attached to the quaternary ammonium nitrogen atom, as well as thosehaving at least one lipophylic quaternary ammonium cation in which thequaternary ammonium. nitrogen atom is one of the nuclear atoms of aheterocyclic ring (the nuclear atoms of which advantageously consist ofcarbon and nitrogen atoms), said ring being devoid of fusedon aromaticrings. I

I have found that the ammonium cation (quaternary or not) advantageouslyshould contain at least one organic group containing a chain of at leasteight members. Advantageously, such members are from the groupconsisting of carbon, oxygen, nitrogen and sulfur atoms. One

'or more aromatic rings, such as a benzene ring for example, can takethe place of one or more ofthe eight or more atoms. Thus, a benzene ringcan take the place of one atom, while a naphthalene ring (two benzenerings fused together) can take the place of two atoms. The atomsattached to the eight or more atoms in the chain (where valence permits)can be hydrogen, oxygen, carbon, or halogen for example. Any aromaticring system in the chain can carry simple substituents. The organicgroup containing a chain of eight or more atoms can be attached directlyto the ammonium nitrogen atom or indirectly thereto by means of a groupof atoms. I have found that cationic ammonium salt surface activesubstances, especially the quaternary type, having an ammonium cationcontaining a lipophylic organic group which contains a chain composed offrom nine to twelve members selected from the group consisting of carbonatoms, oxygen atoms, nitrogen atoms, sulfur atoms and aromatic ringsystems, are advantageously employed.

The anion may be any acid radical, such as chloride, bromide, iodide,p-toluenesulfonate, perchlorate or alkylsulfate for example. Of course,introduction of halide anions into photographic silver halide emulsionsalters the halide concentration in the emulsion and compensating changesin the emulsion may be necessary, if such ammonium salts are employed.For this reason, I ordinarily prefer to employ surface active substancescontaining anions other than halides. Perchlorates andp-toluenesulfonates are advantageously employed;

Following are representative cationic ammonium salt surface activesubstances especially useful in practicing my invention.

1. Tetraalkyl quaternary ammonium salts which can be represented by thefollowing general formula:

wherein at least one of the groups R, R, R" and R' represent an organiclipophylic group containing a chain of at least eight members selectedfrom the group consisting of carbon represented by the following generalformula:

wherein R represents an organic lipophylic group containing a chain ofat least eight members selected from the group consisting of carbonatoms, oxygen atoms, nitrogen atoms, sulfur atoms and aromatic ringsystems and x represents an acid radical or anion.

3. Pyridihium quaternary salts which can be represented by the followinggeneral formula:

wherein R represents an alkyl group, such as methyl, ethyl, butyl orbenzyl for example, one of the groups R and R" represents an organiclipophylic group containing a chain of at least eight members selectedfrom the group consisting of carbon atoms, oxygen atoms, nitrogen atoms,

sulfur atoms and aromatic ring systems while the other of the groups Rand R represents hydrogen or a low molecular weight alkyl group, such asmethyl, ethyl or butyl, and x represents an acid radical or anion.

4. Piperidinium salts which can be represented by the following generalformula:

nsc

R i R wherein one of the groups R and R represents an organic lipophylicgroup, containing a chain of at least eight members selected from thegroup consisting of carbon atoms, oxygen atoms, nitrogen atoms, sulfuratomsand aromatic ring systems, while the other of the R and R groupsrepresents hydrogen or a low molecular weight alkyl group, such asmethyl, ethyl, butyl or benzyl for example, and X represents an acidradical or anion. I

5. Pyrazolium quaternary salts which can be represented by the followinggeneral formula:

nc--c-cm HrC- /}nx I N wherein one of the groups R and R represents anorganic lipophylic group containing a chain benzyl, and X represents anacid radical or anion.

6. Imidazolinlum quaternary salts which can be represented by thefollowing general formula:

wherein one of the R and R groups represents an organic lipophylic groupcontaining a chain of at least eight members selected from the groupconsisting of carbon atoms, oxygen atoms, nitrogen atoms, sulfur atomsand aromatic ring systems while the other of theR and R groupsrepresents a low molecular weight alkyl group such as methyl, ethyl,butyl or benzyl and X represents an acid radical or anion.

The following are representative of organic lipophylic groups containinga chain of at least eight members selected from the group consisting ofcarbon atoms,-oxygen atoms, sulfur atoms and aromatic ring systems:

Octyl. GET-(C1197 Nonyl, C-H (CH2)a(nil1e atom chain) Decyl,CHr-(CHz)w-(t8ll atom chain) Cetyl, CH3(CH2)1s-(sixteen atom chain)Heptoxymethyl, CHr-(CH2)0CH2'-(Ilifl6 atom chain) Undecoxy'methyl,CHI-(CH2)mO-CHa(thirteen atom chain) Butoxyethoxyethyl,CH:(CHz)a-O(CHr)7"O-CHgCH2- (ten atom chain)'ler-butylphenoxyethoxyethyl,

CH; (eight atom+phenyl group chain) FormylphenyloxyethoxyethylOCHzCHz-OCHr-CH:- H (seven atom+phenyl group chain)Phenylphenoxyethoxyethyl (six atom+two phenyl groups chain)Methylphenoxypropoxypropyl cm-Qo-wmnm-wngr (nine atom-l-phenyl groupchain) HOCH2(CH:) l-CHF (eleven atom chain) B-Naphthoxyethoxyethyl Ihave found that pyridinium quaternary salt surface active agents areespecially advantageously employed. The quaternary salt surface activeagents derived from dibenzymethyl and dibenzyethyl amines are alsoadvantageously employed. These dispersing agents tend to produce lesserphotographic fog.

I have found it advantageous to incorporate spectral sensitlzers in thephotographic emulsions prior to incorporation of the perchlorate surfaceactive agents in the emulsions. With surface active agents containingother anions, the order of incorporation of the agent with'respect tothe spectral sensitizer appears to be of small moment.

The quantity of surface active agent which is mostv advantageouslyemployed varies with the nature of the surface active agent and with thenature of the emulsion. Ordinarily the most advantageous concentrationwas found to be between about 20 mg. and about 200 mg. of the surfaceactive agent per gram-mole of silver halide in the amulsion, althoughgreater or smaller concentration can be employed. I have found thatexcesses of the surface active agent are advantageously avoided, sinceexcesses produce fog in the emulsions. For surface active agentscontaining a lipophylic group containing achain of eight to ten members,I have found that as much as about 400 mg. of surface active agent permole of silver halide in the emulsion can ordinarily be employed withoutencountering excessive fog, while with surface active agents containinga lipophylic group containing a chain of eleven to twelve or moremembers, I have found that not more than about 200 mg. of surface activeagent per mole of silver halide should ordinarily be employed.

The optimum range of concentration for any particular surface activeagent is ordinarily fairly narrow and can best be determined byemploying a series of concentrations of the surface active agents,separately in several batches of the same emulsion and determiningthesensitivity of the several emulsions, before and after incorporation ofthe surface active agent, in a conventional manner, well known to thoseskilled in the art. Briefly, the method of determining sensitivity ofemulsions comprises coating the emulsion onto a glass plate to asuitable thickness and drying the coated emulsion, and then testing theresulting photographic plate in a wedge spectrograph and a sensitometer,whereby spectral sensitivity and speed of the emulsion on the plate isdetermined.

When employing spectrally sensitized emulsions, the spectral sensitizersare advantageously employed in about their optimum concentration whichordinarily lies between about 3 mg. and 20 mg. of spectral sensitizerper liter of emulsion containing about 0.25 mole of silver halide,although concentrations above or below the optimum concentration can beemployed. With fine-grain emulsions (which includes most of theordinarily employed silver chloride emulsions), the ratio ofconcentration of sensitizing dye to the concentration of silver halidein the emulsion is advantageously larger than in the coarser grainemulsion, where smaller amounts of sensitizing dye usually give optimumsensitization. The optimum concentration, as above referred to, of asensitizing dye (i. e. the concentration at which greatest sensitivityoccurs) can be readily determined in a mannerwell known to those skilledin the art by measuring the sen- My invention is directed particularlyto the silver-halide developing-out emulsions customarily employed inthe art, including the gelatino- A silverchloride, thegelatino-silver-bromide and the gelatino-silverbromiodide developing-outemulsicns, for example. However, my invention can be employed withsilver halide emulsions wherein the carrier is other than gelatin, forexample a resinous or cellulosic substance which has substantially nodeleterious eifect on the light-sensitive materials in the emulsions.

As spectral sensitizers (sensitizing dyes), only those which arenon-acidic can be employed in practicing my invention. sensitizing dyes,such as Congo red, which disperse in water to give a colored anion, i.e. acidic sensitizing dyes, appear to interfere with the surface activeagent, with the result that neither the acid dye nor the surface activesubstance exert a. substantially beneficial effect on the emulsion. Asnon-acidic sensitizing dyes, I include all the known neutral and basicsensitizing dyes, i. e. those sensitizing dyes which do not give coloredanions. Some of these non-acidic sensitizing dyes, such as the cyaninedyes, give colored cations. Exemplary of the non-acidic sensitizing dyesare the sensitizing cyanine dyes (see, for example United States Patents1,846,300; 1,846,301; 1,846,302; 1,846,303 and 1,846,304 each datedFebruary 23, 1932, United States Patent 1,861,836, dated June 7, 1932,United States Patent 1,939,201, dated December 12, 1933, United StatesPatent 1,942,- 854, dated January 9, 1934, United States Patent1,957,869, dated May 8, 1934, United States Patent 1,962,124, dated June12, 1934, United States Patent 1,969,446, dated August 7, 1934, UnitedStates Patent 1,973,462, dated September 11, 1934; United States Patent1,990,507, dated February 12, 1935, United States Patent 2,094,580,dated October 5, 1937, United States Patent 2,112,140, dated March 22,1938 and French Patent 757,813, published January 5, 1934), thesensitizing merocyanine dyes (see United States Patent 2,078,233, datedApril 27, 1937, United States Patent 2,089,729, dated August 10, 1937,United States Patent 2,153,169, dated April 4, 1939 and United StatesPatents 2,177,401; 2,177,-

sensitizing hemicyanine dyes (see United States Patent 2,166,736, datedJuly 18, 1939) and the sensitizing hemioxonol dyes (see United StatesPatent 2,165,339, dated July 11, 1939 and French Patent 841,632,published May 24, 1939) While the process of my invention is subject tovariation particularly as respects the nature and quantity of aqueousdispersing and or wetting agent employed, the nature and quantity of thespectral sensitizer employed, if any, the nature of the silver halideemulsion employed and the manner of incorporating the dispersing agentand spectral sensitizer (if any) in the emulsions, the following examplewill serve to illustrate the manner of obtaining my new emulsions. Thisexample is not intended to limit my invention.

Example Into one liter of a flowable finished washedgelatino-silver-bromiodide emulsion containing about 0.32 mole oi silverbromide, were incorporated, slowly with stirring, a concentrated methylalcoholic solution of 2,2'-diethyl-8methyl-3,4,3',4'-dibenzothiacarbocyanine chloride. Sufilcient of thealcoholic solution was added to incorporate about15 mg. of thecarbocyanine chloride in the emulsion.

To the resulting mixture were added, slowly and with stirring, a 1% (byweight) aqueous solution of lauryltriethylammonium perchlorate.Sufllcient of the aqueous solution was added to incorporate about mg. ofthe perchlorate in the emulsion.

Photographic elements can be made from emulsions prepared in the abovemanner by coating the emulsions to a suitable thickness on a suitablesupport and drying the coated emulsion, in a manner well known to thoseskilled in the art. Suitable supports are, of course, glass,photographic paper support and photographic film support. Thephotographic film support may, of course, be of cellulose acetate,cellulose nitrate or any other suitable cellulose derivative, or be ofany suitable resinous material, such as a polyvinyl acetal resinousmaterial for example. My new emulsions are advantageously coated onglass support.

The following table contains a summary of some of the more practicalresults I have ob- 402 and 2,177,403, dated October 24, 1939), the 50tained by my invention.

Table White light Emulsion sensitizing dye Surface active agent FogSpeed Gamma Mg. per liter ofemulaion Mg. per liter of emulsionGelatino-silver-bromiodide (about 2, 2'-diethyl-8metliyl-3, 4, 3, 4'-di-None 1.050 1.53 0.08

0.32 mole of silver halide per liter). benfi ihiacarbocyanine chloride,15 (clear) mg. 1 er. Do ..do Lauryltriethyl-ammonium perchlo- 1,320 1.720.10

rate, 50 rug/liter. (clear) Do 2, 2-diethyl-8-methylthiacarbocya- None.4 1,260 1. 47 0.06

nine bromide, 15 mg./liter. (cl ar) Do do Lauryltriethyl-ammoniurnperchlo- 1.700 1.56 0.11

rate, 50 mgJliter. (clear) Do 3-ethyl-5-(2-ethylbenzoxazolyidene- None775 1.01 0.06

ethylidene)-rhodanine, l0 mgJIiter. (clear) Do .doLauryltriethyl-ammonium perchlo- 1,070 1.53 0.08

rate, 50 mg./1iter. Do 2-diphenylarnino-5-(2-ethyl-l-benzo- None 1. 5101.50 0.08

thiazylidene-ethylidene)-4-(5)-thia- (clear) zolone, l5 mgJliter. Do oN-heptoxymethyl pyridiniuni pcr- 1.100 1.37 0.08

chlorate, 30 lug/liter. (clear) Do 2-[4-(l-piperidyl-A,=-butadienyl)]-fl- None .1 890 0.94 0. 03

ingphthathiazole ethiodide, 50 mg./ (clear) 1 er. Do -do N-heptoxymethylpyridiniurn per- 1.100 0.92 0.08

chlorate, 30 mg./liter. (clear) Do 3-ethyl-5-[ -(l-pipcridyl)a1lylidene1- None 630 1. 33 0.10

rhodanine, 15 mg.lliter. (clear) Do None N-heptoxymethyl-pyridinium per-930 1.27 0.10

chlorate. (clear) (White light minus White light blue) No. 12 Emulsionsensitizing dye Surface active agent Fog filter Speed Gamma Speed GammaGelatino-silver-bromiodlde 2,2-di1nethyI-S-ethyl-thie- None 935 0.00 .03265 1.1

(0.26 mole silver halide per iigrbotiyiizgline br m $3.1 "00F. Nggyl nyridinium perchlorate, 1,200 0.91 .10 330 0,00

"""" mg. i or.

Nonyl pyridinium perchlorate, 1,200 0.96 .10 445 0.86

50 trig/liter. 4 Decyl pyridinium perchlorate, 1,230 1.02 .10 390 1.0830 mg./liter. a-nonyl-N-methyl pyridinium 1,200 0.94 .08 425 0.99

rchlorate 20 mg./l1ter. pert. butyl phenoxy-ethoxy- 1,380 0.84 .09 3050.87

ethyl p ridinium perchlorate 30 mg./l ter. N-nonyl piperidinium methyl1,000 0.97 .10 295 1.00

istioluene sulionate, 30 mg./

r. Hexoxymethyl pyridinium per- 1,100 0.95 .10 325 1.03.

chlorate, 50 mg./l1 ter. Hegtoxymethyl pyr dinium per- 1, 120 0. 97 11390 0.99

c lorate, 50 mg./l1ter. Octoxymethyl pyridinium per- 1,230 1.05 .11 5251.00

chlorate 30 mg./liter. Nonoxyethyl pyridinium per- 1,750 0.98 16 6301.05

chlorate, 30 mg./liter. N-decyl-l,3 o-trimethyl pyrazo- 1, 350 0. 99 .10465 0. 94

lium perchlorate 30 rug/liter. N-Carbomonoxymethyl pyri- 1,180 0.92 .09455 0.94

iiitgium perchlorate, 30 mg./

1 r. 1 none e NODB 720 1.08 .05 Do $1 132) Heptoxymethylpyridinium per-870 1.07 .05

chlorate, 20 mg./liter. Heptoxymethylpyridinium per- 950 1. 04 05chlorate 30 mg./liter. Do Ethylene his dioxymcthyl pyri- 930 1. .06

""""""""""""" iiiigium perchlorate, mg./

r. Ethylene bis dioxymethylpyril 100 1.06 .06 Do ditrgium perchlorate,mg./

r. n-Nonyl pyridinium perchlo- 1 000 1.03 .05 Do rate, 30 mg./liter. Dodo ay -N-methyl pyridinium 1,100 1.03 .05

""""""""""" perchlorate, 15 mg./liter.

The improvement produced by my invention may still be more readilyappreciated from an inspection of a graphic representation.

The accompanying drawing is a reproduction of two spectral sensitivitycurves. Curve A represents the spectral sensitivity of a gelatino silverbromiodide emulsion (about 0.25 mole of silver halide per liter ofemulsion) containing sensitizing dyes such as thiacarbocyanine dyes and2'-cyanine dyes as described in Mees U. S. Patent 2,158,882, granted May16, 1939.

Curve B represents the spectral sensitivity of the same dyed emulsionbut containing in addition a cationic surface active salt in accordancewith the present invention in the concentration of approximately 15 mg.per liter of emulsion.

The spectral sensitivity curves were determined as described by Jonesand Sandvik in the Jour. of the Optical Soc. of America, vol. 12, page401,

It will be seen from a consideration of these curves that not only isthe spectral sensitivity of curve B an improvement over curve A, butthis improvement extends over the entire curve and more or less the samedegree of improvement. It is in these latter features that my inventionconstitutes a rather marked departure from the prior art.

It will be observed that in the tables I have described a. number ofexamples of perchlorate derivatives, inasmuch as this particularderivative is preferred, because of the improved properties thereof.However, it is also to be observed that the p-toluene-sulfonates andother derivatives such as bromides and the like are also satisfactory inthe practicing of my invention.

These derivatives may be produced by a variety of methods and obtainedfrom any source assuming, of course, that the materials meetphotographic specifications.

However, I prefer to obtain perchlorate derivatives by the novel methoddescribed in Allen and Wilson application, filed of even date, entitledSurface active materials."

The sulfonates, bromides and other derivatives may be satisfactorilyproduced by known methods; hence, reference to a description thereof isunnecessary.

It is apparent from the foregoing that my invention is susceptible ofsome modification; hence, I do not wish to be restricted exceptinginsofar as may be necessitated by the prior art and the spirit of theappended claims.

What I claim as my invention and desire to be secured by Letters Patentof the United States'is:

1. A photographic silver halide emulsion sensitized with a cationicsurface active ammonium salt.

2. A photographic silver halide developing-out emulsion sensitized witha cationic surface active ammonium salt.

3. A photographic gelatino-silver-halide emulsion sensitized with acationic surface active ammonium salt.

4. A photographic gelatino-silver-halide developing-out emulsionsensitized with a cationic surface active ammonium salt.

x 5. -A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active ammonium salt.

6. A photographic Silver halide emulsion sensitized with a cationicsurface active quaternary emulsion sensitized with a cationic surfaceactive quaternary ammonium salt.

8. A photographic gelatino-silver-halide emulsion sensitized with acationic surface active quaternary ammonium salt.

9. A photographic gelatino-silver-halide developing-out emulsionsensitized with a cationic surface active quaternary ammonium salt.

10. A photographic silver halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active quaternary ammonium salt.

11. A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active quaternary ammonium salt.

12. A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active tetra-alkyl quaternary ammoniumsalt.

13. A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active pyridinium alkyl quaternarysalt.

14. A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active N-alkylpiperidinium quaternarysalt.

15. A photographic gelatino-silver-halide emul-' sion sensitized with asupersensitizing combination of a non-acidic sensitizing dye togetherwith a cationic surface active quaternary ammonium salt, the cation ofwhich contains at least one organic group containing a chain of at leasteight members selected from the group consisting of carbon atoms, oxygenatoms. sulfur atoms, nitrogen atoms and benzene nuclei.

16. A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of a non-acidic sensitizing dye togetherwith a cationic surfaceactive quaternary ammonium, salt, the cation ofwhich contains at least one organic group containing a chain of fromnine to twelve members selected from the group consisting of carbonatoms, sulfur atoms, oxygen atoms, nitrogen atoms and benzene nuclei.

17. A photographic gelatino-silver-halide emulsion sensitized with atleast one non-acidic sensitizing dye and containing, in a concentrationof from about 20 to about 400 milligrams per grammole of silver halidein the emulsion, a cationic surface active quaternary ammonium salt, thecation of which contains at least one organic group containing a chainof from 9 to 10 members selected from the group consisting of carbonatoms, sulfur atoms, oxygen atoms, nitrogen atoms and benzene nuclei.

18. A photographic gelatino'silver-halide emulsion sensitized with atleast one non-acidic sensitizing dye and containing, in a concentrationof from about 20 to about 200 milligrams per grammole of silver halidein the emulsion, a cationic surface active quaternary ammonium salt, thecation of which contains at least one organic group containing a chainof from 11 to 12 members selected from the group consisting of carbonatoms, sulfur atoms, oxygen atoms, nitrogen atoms and benzene nuclei.

19. An undyed gelatino silver halide emulsion containing, at least, onecationic surface active ammoniuma salt in a concentration equal to lessthan 400 milligrams per gram-mole of silver halide in the emulsion.

BURT H. CARROLL.

